A conventional bathroom air-conditioner using a heat pump has worked this way: A first heat exchanger of the heat pump radiates or absorbs heat to/from the air drawn from the outside of the bathroom, and then blows out the air into the bathroom. A second heat exchanger of the heat pump absorbs or radiates heat from/to air evacuated from the bathroom to the outdoors. The bathroom has been thus air-conditioned (refer to, e.g. Patent Document 1).
The foregoing air-conditioner collects the heat from the air to be discharged from the bathroom to the outdoor, and gives heat to another air drawn from a place other than the bathroom, thereby air-conditioning the bathroom. A continuous operation of this air-conditioner sometimes generates a difference in enthalpy between the air drawn from a place other than the bathroom and the air in the bathroom. In such a case, a part of the heat having undergone the air-conditioning of the bathroom leaks to the outdoor, so that a loss in heat collection becomes greater, and the efficiency of the air-conditioner lowers.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2005-180712